Converter



Nov. 6, 1934. H. THOLSTRUP CONVERTER Filed Sept. 12, 1952 Patented Nov. 6, 1934 CONVERTER Henry Tholstrup, Dayton, Ohio, assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application September 12, 1932, Serial No. 632,703

9 Claims. (Cl. 171-97) This invention relates to a means for producing a pulsating or alternating current from a direct current source, and more particularly to a means for accomplishing the result that is relatively simple in construction and capable of flexibility of design.

The extensive use of radio devices on moving vehicles such as automobiles and airplanes has brought about a desire for a means of producing the various potentials and currents necessary in the operation of the devices that is light, compact, and capable of a flexibility of design that will make it possible to suit it to the purpose. And, other possible uses also make the development of esuch a means desirable.

Since alternating or pulsating currents are more easily adapted to transformation, many devices have been devised to produce alternating currents from a direct current source. Some are massive a and ponderous, and others must operate under constant conditions in order to produce a constant frequency alternating current.

It 'is therefore an object of this invention to provide a means for converting direct current to pulsating or alternating current, or to a direct current of higher voltage, that may be made up into a light weight compact unit.

It is also an object of this invention to provide a means for producing an alternating or pulsating current of substantially constant frequency for all normal operating conditions.

Another object of this invention is to provide a means for producing alternating, pulsating, or higher voltage direct current from a direct ourl rent source without the aid of mechanically moving parts.

Still another object of this invention is to provide a converter unit having means for predetermining the frequency of the alternating or pulsating potential.

A further object of the invention is to provide a converter unit that is capable of conveniently and economically producing an alternating or pulsating current having a frequency high enough to necessitate only a relatively small amount of iron in a transformer utilized therewith.

Further objects and advantages of the present invention Will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawing: ;Fig. 1 discloses a circuit for obtaining a pulsating current from a direct current source, and a transforming and rectifying system.

Fig. 2 discloses a circuit modification applicable to the circuit of Fig. 1 for applying additional potential to elements of part of the tubes of Fig. 1.

Fig. 3 discloses still another modification applicable to the circuit of Fig. l for applying additional potential to the elements of the tubes shown in Fig. 1.

With particular reference to Fig. 1, a source of direct current has its terminals connected across a heater element 12 of a thermionic tube through a resistance i l. A. cathode 16 of the thermionic tube 20 is connected to one terminal of the direct current source 10, intermediate that source and the heater 12. The other terminal of the direct current source 10 is connected to an anode 18 of the thermionic tube 20 through an inductance 22. A condenser 24 is connected across the inductance 22 to form a resonant circuit 82. A control electrode or grid 26 of the thermionic tube 29 is connected to the same terminal of the direct current source 10 that the cathode 16 is connected to, and that connection is made through an inductance 28. A condenser 30 is connected across the inductance 28 to form a resonant circuit 84. The inductances 22 and 28 are magnetically coupled, and preferably have a magnetic core 32. The thermionic tube 20 and the elements associated therewith, including the inductances 22 and 28 and condensers 24 and 30 form an oscillatory circuit or oscillation generator.

Thermionic tubes at and 36 have filament elements 38 and 40 respectively, connected in parallel and across the terminals of the direct current source 10 through a resistance 42. Control electrodes 44 and 46 of the thermionic tubes 34 and 36 respectively, are connected to the extremities of an inductance 48 which inductance is magnetically coupled with the inductance 28. A mid-tap 50 of the inductance 48 is connected to a terminal of the direct current source 10 intermediate that source and the filaments 38 and 4.0. Anodes 52 and 54 of the thermionic tubes 34 and 36 respectively, are connected to extremities of a primary winding 56 of a transformer 58. A mid tap 60 of the primary winding 56 is connected to a terminal of the direct current source 10 intermediate that terminal and the inductance 22. The transformer 58 has a magnetic core and a secondary winding 62, the extremities of which are connected to terminals of rectifiers 64 and 66. The other terminals of rectifiers fi l and 66 are connected together, and to the side of a circuit of the filaments 38 and 40 that is connected to the direct current source 10. This common connection of the rectifiers 64 and 66 also has an output lead 68 connected thereto. A mid-tap 72 of the secondary winding 62 is connected to another output lead 70. The transformer 58 may also have another secondary winding '74 provided with leads '76 and 78, if desirable.

With particular reference to Fig. 2, reference numerals in this figure which are similar to those in Fig. 1 refer to similar parts. The similar parts of Figs. 1 and 2 perform similar functions in the operation of the circuit. However, in the modification disclosed in Fig. 2, the mid-tap of the primary winding 56 of the transformer 58 is connected to one terminal of a direct current source 100. The other terminal of the direct current source 100 is connected to a lead 102 that is adapted for connection to a terminal of the direct current source 10 of Fig. l at a point intermediate that source and the inductance 22. Leads 104 and 106 connected to control electrodes 44 and 46 respectively, are adapted for connections such as shown in Fig. 1, to the extremities of the inductance 48. Lead 108 is adapted for connection to a termi nal of the direct current source 10.

With particular reference to Fig. 3, the parts bearing reference numerals similar to those of Figs. 1 and 2 are similar, and perform similar functionsl -to those of Figs. 1 and 2. In this modificatioh', however, the mid tap 60 of the primary winding 56 is connected to one end of the inductance 22 intermediate that inductance and a direct current source 200. The direct current source 200 has one terminal connected to a terminal of the direct current source 10 so that the two sources are in series. The'heater 12 is connected across the source 10 through a resistance 14, and the filaments 38 and 40 are connected in parallel, and across the source 10 through a resistance 42, as in Fig. 1. The additional potential supplied by the source 200 is then applied to the anode 18 through the inductance 22, and to the anodes 52 and 54 through the mid-tap 60 and primary winding 56.

In the operation of the circuits according to the preferred modification disclosed, the current for heating the heater 12 and filaments 38 and 40 is supplied by the direct current source 10. In the modification disclosed in Fig. 1, the potentials for the anodes 18, 52 and 54 are supplied also from the direct current source 10. When in operation, the thermionic tube 20 will oscillate at a fixed frequency dependent upon the values of the inductances 22 and 28, the capacity of condensers 24 and 30 and the constants of the magnetic core 32. The magnetic core 32 is preferably used because the desirable frequency of oscillation of a circuit used in this manner is rather low for such a circuit, and the magnetic core permits a reduction of the physical dimensions of the inductances necessary in obtaining a desired frequency. It is understood however, that by making the frequencyhigh with respect to usual power frequencies, the core dimensions of the transformer 58 will be reduced.

The inductance 48, magnetically coupled with the inductance28 necessarily has an alternating potential induced therein of the same frequency as the oscillating frequency of the oscillatory cir- (Suit. Since the extremities of the inductance 48 are connected to control electrodes 44 and 46 of the thermionic tubes .34 and 36 respectively, al-

ternating potentials will be applied to those control electrodes, and the potentials of the electrodes will be 180 out of phase. Characteristics of the thermionic tubes 34 and 36 are such that the potentials applied to the control electrodes 44 and 46 from the inductance 48 will determine whether or not current may flow from the anode 52 to the filament 38 and from the anode 54 to the filament 40. Since the potentials of the control electrodes are continually varying, and are 180 out of phase, the current flow through the tubes 34 and 36 will be pulsating and also approximately 180 out of phase. This action causes a pulsating current flow in the primary winding 56 which in turn induces an alternating current in the secondary winding 62.

By connecting a half-wave rectifier to each of the extremities of the secondary winding 62 and connecting an output lead to a mid-tap '72, the output current of the secondary winding 62 may be rectified and applied to any suitable load such as a radio device. If the transformer used is a step-up transformer, the circuit provides a means for obtaining a high voltage direct current supply from a lower voltage direct current. source if therectifiers are used, and a means for ob taining a high voltage alternating current from the lower voltage direct current supply if the rectifiers are not used. However, the ratio Qf the transformer 58 is not particularly material, and the scope of the invention is not limited to any particular ratio or variety of transformer. Neither is the invention deemed to be limited to the particular oscillatory circuit disclosed, because other circuits are known to those skilled in the art which would perform practically the same function if properly designed.

In some cases, and particularly those cases in which the voltage of the direct current source 10 is high enough to permit the tube 20 to operate satisfactory, but is not high enough to permit satisfactory operation of the tubes 34 and 36, and additional direct current source as the source 100 in Fig. 2 may be inserted as shown in and described for Fig. 2, to increase the anode potentials of the tubes 34 and 36.

In some cases, and particularly when the'voltage of the direct current source 10 is too low to permit satisfactory operation of either the tube 20 or the tubes 34 and 36, an additional source of direct current such as the source 200 may be added as shown in and described for Fig. 3,.

In any of the modifications, tubes such as, or similar to, those lmown as Thyratrons are preferable for the thermionic tubes 34 and 36, especially where any appreciable amount of current is necessary or desirable in the primary circuit of the transformer. It is not desired to limit the invention to that particular type of tube however, because if only very small currents. are necessary in the transformer primary circuit, other present types of tubes would be operable, and with the rapid development of vacuum tubes, a tube even more suitable or efiicient than the Thyratron tubes might be developed.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows.

1. A means for obtaining alternating current from a direct current source, including in combination, a direct current source, means for generating oscillations having a thermionic tube therein the space current for which is provided by said direct current source, thermionic devices at least a portion of the space currentof which is provided by said direct current source, output electrodes in said thermionic devices, a transformer having a primary winding connected to said output electrodes, and m ans including said thermionic devices for controlling the current fiow from said direct current source to said primary winding.

2. A means for obtaining alternating current from a direct current source, including in combination, a direct current source, means for generating oscillations having a thermionic tube therein that receives energy from said direct current source, a second direct current source, thermionic devices that receive energy from both of said direct current sources, output electrodes in said thermionic devices, a transformer having a primary winding connected to said output electrodes, and means including said thermionic devices for controlling the current ilow from said direct current source to said primary winding.

3. A means for obtaining alternating current from a direct current source, including in combination, a direct current source, a hot cathode thermionic tube having an anode and control electrode therein and connected in an oscillatory circuit, means for supplying the cathode heating current and anode and control electrode potentials from said direct current source, control tubes having output and control electrodes therein, means for supplying said output electrode potentials from said direct current source, a transformer having a primary winding, and means including said control tubes for controlling the current flow from said direct current source to said primary winding in response to the oscillating potentials applied to the control electrodes of said control tubes from said oscillatory circuit.

4. A means for obtaining alternating current from a direct current source, including in combination, a direct current source, a hot cathode thermionic tube having an anode and control electrode therein and connected in an oscillatory circuit, a second source of direct current, means for supplying the cathode heating current from the first mentioned source and the anode potential from both of said sources, control tubes having output and control electrodes therein, means for supplying the output electrode potentials from both of said sources, a transformer having a primary winding, and means including said control tubes for controlling the current flow from one of said sources to said primary winding.

5. A means for obtaining alternating current from a direct current source, including in combination, a direct current source, a hot cathode thermionic tube having an anode and control electrode therein and connected in an oscillatory circuit, means for supplying the cathode heating current and anode and control electrode potentials from said source, a second source of direct current, control tubes having output and control electrodes therein, .neans for supplying the output electrode potentials from both of said sources in additive relation, a transformer having a primary winding, and means for controlling the current flow from one of said sources to said primary winding.

6. In an electrical network for transforming low voltage direct current into high voltage direct current, an oscillation generator comprising in combination a source of comparatively low voltage direct current, an electronic tube having an anode, a cathode and a control electrode, a connection including the primary winding, a coupling transformer between the anode and the positive terminal of said source, a connection between the cathode and the negative terminal of said source, a heating circuit for said cathode connected across said source through a current impeding device, a connection including the secondary of said transformer between the control grid and said cathode, a pair of electronic tubes, push-pull input and output circuits therefor, a split winding in aid push-pull input circuit symmetrically coupled to one of said transformer windings, a split winding in said push-pull output circuit, a rectifier circuit provided with an input and an output circuit, means for coupling said push-pull output circuit to the rectifier input circuit through said output split winding circuit, a connection between a point of said pushpull output circuit split winding and the positive terminal of said source, and a connection between a point of said push-pull input circuit split winding and the negative terminal of said source.

'7. A system as recited in the next preceding claim wherein a booster source of potential is provided in the connection between the anode of the first named electronic tube and the positive terminal of the source.

8. A system as recited in claim 6 wherein a booster source of potential is provided in the conn ction between the push-pull output split winding and the positive terminal of the source.

9. In an electrical network for changing low voltage direct current into high voltage direct current suitable for energizing electronic tubes of radio receivers and the like, an oscillation generator circuit comprising in combination, a source of comparatively low voltage direct current, an electronic tube having an anode, a cathode and a control electrode, means for energizing said cathode comprising connections to said source, input and output circuits for said tube, said output circuit including a connection between said anode and cathode including the primary of a coupling transformer and said source in series, said input circuit including a connection between the control electrode and the cathode including the secondary of said coupling transformer, said coupling transformer acting to link said input and output circuits to facilitate the transfer of energy from said output circuit to said input circuit for producing oscillations, means associated with said generator circuit for determining the frequency of oscillations generated thereby, a pair of electronic tubes each thereof including anode, cathode and grid electrodes, push-pull input and output circuits therefor, means for energizing said two last named tubes including connections to said source for energizing the cathodes thereof and means for including said source in the common portion of said push-pull output circuit to thereby energize the anodes of said tubes with respect to the cathodes thereof, a rectifier circuit including input terminals and output terminals and means for coupling the push-pull output circuit to said rectifier input terminals, said rectifier output terminals being adapted to be connected to a utilizing circuit.

HENRY THOLSTRUP. 

